Among various semiconductor devices, the amount of heat generated in a high power control power device used for controlling electric automobiles, electric vehicles and the like is large. Thus, a power module substrate obtained by bonding metal plates, respectively, as a circuit layer and a metal layer, to one surface (first surface) and the other surface (second surface) of a ceramic substrate composed of, for example, AlN (aluminum nitride) or the like as a substrate on which the power device is mounted has been widely used in the related art.
Such a power module substrate is used to form a heat-sink-attached power module substrate by bonding a heat sink having excellent thermal conductivity to the side of the second surface of the ceramic substrate. In addition, a semiconductor device, as a power device, is mounted on the circuit layer with a soldering material interposed therebetween to form a heat-sink-attached power module.
As the above-described power module substrate, for example, PTL 1 discloses a power module substrate including a metal layer having a 4N aluminum (4N—Al) layer bonded to a lower surface of a ceramic substrate and a 2N aluminum (2N—Al) layer bonded to the 4N aluminum layer. The metal layer of the power module substrate and a heat radiating plate (heat sink) composed of Cu are bonded to form a heat radiating plate-attached (heat-sink-attached) power module substrate.
In addition, PTL 2 discloses a power module substrate including a metal layer composed of a 2N aluminum layer that is bonded to a lower surface of a ceramic substrate.
PTL 3 discloses a power module substrate including a metal layer composed of a Cu layer that is bonded to a lower surface of a ceramic substrate.